针对无螺纹自锚式锚杆的承载特性,基于B样条物质点法(B-spline Material Point Method,BSMPM),引入了库伦摩擦模型、指数模型和双曲线模型,发展了土体-锚杆耦合界面接触模型,开展了锚杆的竖向和水平拉拔模拟,并与已有试验结果或理论解...针对无螺纹自锚式锚杆的承载特性,基于B样条物质点法(B-spline Material Point Method,BSMPM),引入了库伦摩擦模型、指数模型和双曲线模型,发展了土体-锚杆耦合界面接触模型,开展了锚杆的竖向和水平拉拔模拟,并与已有试验结果或理论解进行对比.结果表明:(1)B样条物质点法能够准确计算土体-锚杆耦合问题,引入三种接触模型下的耦合模型所得锚杆竖向拉拔模拟结果均与已有试验结果吻合较好,所得锚杆水平承载力特征值与理论解相对误差在合理范围内,指数接触模型、摩擦接触模型和双曲线接触模型的相对误差分别为12.03%、13.04%和13.19%;(2)水平荷载下锚杆变形由锚杆与土体的相对刚度主导,长径比增加至30时,锚杆变形特征由刚性转变为弹性;(3)随着锚杆直径的增大,水平变形系数呈幂指数减小,锚杆的水平承载力呈负指数衰减型曲线增长规律,锚杆直径由100 mm增大至400 mm,水平承载力提升83%(10.3 kN→18.87 kN).研究结果验证了B样条物质点法在土体-锚杆耦合问题研究上的可行性,为土体-结构耦合问题研究提供了可靠分析方法.展开更多
The recirculating planetary roller screw mechanism(RPRSM)is a transmission mechanism that engages the screw and nut threaded by multiple grooved rollers.In this paper,frstly,the design method of RPRSM nut threadless a...The recirculating planetary roller screw mechanism(RPRSM)is a transmission mechanism that engages the screw and nut threaded by multiple grooved rollers.In this paper,frstly,the design method of RPRSM nut threadless area is proposed,and the equations related to the structural parameters of nut threadless area are derived.On this basis,the cross-section design method of roller,screw and nut is constructed according to the actual situation of engagements between the screw/nut and the roller.By adjusting the gap between the two beveled edges and that between the arc and the beveled edge,the accuracy of the thread engagements between the screw/nut and the roller can be improved.Secondly,to ensure the engagements of the screw/nut and the roller,the distance equation from the center surface of the diferent rollers to the end surface of cam ring is given.Thirdly,combined with the working principle and structural composition of RPRSM,the component model is established according to its relevant structural parameters,and the virtual assembly is completed.Finally,the 3D model is imported into the ADAMS simulation software for multi-rigid body dynamics.The dynamic characteristic is analyzed,and the simulated values are compared with the theoretical values.The results show that the contact forces between the screw/nut and the roller are sinusoidal,mainly due to the existence of a small gap between the roller and the carrier.The maximum collision forces between the roller and cam ring are independent from load magnitude.Normally,the collision force between the roller and the carrier increases as the load increases.When RPRSM is in the transmission process,the roller angular speed in nut threadless area begins to appear abruptly,and the position of the maximum change is at the contact between the roller and the convex platform of cam ring.The design of the nut threadless area and the proposed virtual assembly method can provide a theoretical guidance for RPRSM research,as well as a reference for overall performance optimization.展开更多
文摘针对无螺纹自锚式锚杆的承载特性,基于B样条物质点法(B-spline Material Point Method,BSMPM),引入了库伦摩擦模型、指数模型和双曲线模型,发展了土体-锚杆耦合界面接触模型,开展了锚杆的竖向和水平拉拔模拟,并与已有试验结果或理论解进行对比.结果表明:(1)B样条物质点法能够准确计算土体-锚杆耦合问题,引入三种接触模型下的耦合模型所得锚杆竖向拉拔模拟结果均与已有试验结果吻合较好,所得锚杆水平承载力特征值与理论解相对误差在合理范围内,指数接触模型、摩擦接触模型和双曲线接触模型的相对误差分别为12.03%、13.04%和13.19%;(2)水平荷载下锚杆变形由锚杆与土体的相对刚度主导,长径比增加至30时,锚杆变形特征由刚性转变为弹性;(3)随着锚杆直径的增大,水平变形系数呈幂指数减小,锚杆的水平承载力呈负指数衰减型曲线增长规律,锚杆直径由100 mm增大至400 mm,水平承载力提升83%(10.3 kN→18.87 kN).研究结果验证了B样条物质点法在土体-锚杆耦合问题研究上的可行性,为土体-结构耦合问题研究提供了可靠分析方法.
基金Supported by National Natural Science Foundation of China(Grant Nos.52065053,51875458)Natural Science Foundation of Inner Mongolia(Grant No.2020BS05003)Inner Mongolia Science and Technology Project(Grant No.2020GG0288).
文摘The recirculating planetary roller screw mechanism(RPRSM)is a transmission mechanism that engages the screw and nut threaded by multiple grooved rollers.In this paper,frstly,the design method of RPRSM nut threadless area is proposed,and the equations related to the structural parameters of nut threadless area are derived.On this basis,the cross-section design method of roller,screw and nut is constructed according to the actual situation of engagements between the screw/nut and the roller.By adjusting the gap between the two beveled edges and that between the arc and the beveled edge,the accuracy of the thread engagements between the screw/nut and the roller can be improved.Secondly,to ensure the engagements of the screw/nut and the roller,the distance equation from the center surface of the diferent rollers to the end surface of cam ring is given.Thirdly,combined with the working principle and structural composition of RPRSM,the component model is established according to its relevant structural parameters,and the virtual assembly is completed.Finally,the 3D model is imported into the ADAMS simulation software for multi-rigid body dynamics.The dynamic characteristic is analyzed,and the simulated values are compared with the theoretical values.The results show that the contact forces between the screw/nut and the roller are sinusoidal,mainly due to the existence of a small gap between the roller and the carrier.The maximum collision forces between the roller and cam ring are independent from load magnitude.Normally,the collision force between the roller and the carrier increases as the load increases.When RPRSM is in the transmission process,the roller angular speed in nut threadless area begins to appear abruptly,and the position of the maximum change is at the contact between the roller and the convex platform of cam ring.The design of the nut threadless area and the proposed virtual assembly method can provide a theoretical guidance for RPRSM research,as well as a reference for overall performance optimization.
